Package cooled with cooling fluid and comprising shielding layer

ABSTRACT

A package which comprises at least one electronic chip, an encapsulant encapsulating at least part of the at least one electronic chip, and a shielding layer on at least part of an external surface of the encapsulant configured for shielding an interior of the package with regard to cooling fluid for removing thermal energy from the at least one electronic chip.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to a package, to an electronic device, toa vehicle, to a method of use, and to methods of manufacturing.

Description of the Related Art

A power module, for instance for automotive applications, provides aphysical containment for power components, usually power semiconductordevices in form of electronic chips comprising one or more integratedcircuit components. Examples of integrated circuit components of powermodules are an insulated-gate bipolar transistor (IGBT), and a diode.

There is still potentially room to improve reliability of a packagewhile efficiently removing heat.

SUMMARY OF THE INVENTION

There may be a need for a package allowing for an efficient removal ofheat generated during operation while ensuring reliability of thepackage.

According to an exemplary embodiment, a package is provided whichcomprises at least one electronic chip, an encapsulant encapsulating atleast part of the at least one electronic chip, and a shielding layer onat least part of an external surface of the encapsulant configured forshielding an interior of the package with regard to cooling fluid forremoving thermal energy from the at least one electronic chip.

According to another exemplary embodiment, an electronic device isprovided which comprises a package having the above mentioned features,and a cooling member configured for being mounted on the package tothereby delimit, together with the package, a cooling cavity foraccommodating cooling fluid for cooling the package.

According to still another exemplary embodiment, a vehicle is providedwhich comprises a package or an electronic device having the abovementioned features.

According to yet another exemplary embodiment, a method of manufacturinga package is provided, wherein the method comprises encapsulating atleast part of at least one electronic chip by an encapsulant, andforming a shielding layer on at least part of an external surface of theencapsulant and configuring the shielding layer for shielding aninterior of the package with regard to cooling fluid for removingthermal energy from the at least one electronic chip.

According to yet another exemplary embodiment, a method of manufacturingan electronic device is provided, wherein the method comprises forming apackage having the above mentioned features, and mounting a coolingmember on the package to thereby delimit, together with the package, acooling cavity for accommodating cooling fluid for cooling the package.

According to yet another exemplary embodiment, a package having theabove mentioned features or an electronic device having theabove-mentioned features is used for an automotive application.

An exemplary embodiment may have the advantage that the removal of heatgenerated by the one or more electronic chips during operation of thepackage may be highly efficient as a consequence of a direct coolingarchitecture by a fluidic (i.e. liquid and/or gaseous) cooling fluid tobe brought in contact with an exterior surface of the package. At thesame time, the provision of a shielding layer on at least a part of theencapsulant's exterior surface which would otherwise be in directcontact with the cooling fluid (i.e. at least on the surface portion ofthe encapsulant contributing to the definition of the cooling cavity)may safely prevent any undesired ingress of cooling fluid into aninterior of the (in particular mold-type) encapsulant material.Conventionally, such a penetration of moisture or the like into aninterior of a package may result in electric instability (in particularthe danger of short-circuiting) and/or mechanical instability (forinstance delamination). Simultaneously and synergetically with theefficient heat removal capability and the high reliability of thepackage, it is thereby made possible by exemplary embodiments of theinvention that the encapsulant covered by the shielding layer can definepart of the cooling fluid exposed exterior surface of the package sothat the surface area defined by costly materials (such as a heatremoval body which may be embodied as DCB substrate) of the package canbe reduced. Thus, a highly efficient cooling performance and a highreliability of the package in terms of its electrical and mechanicalbehaviour may be combined with a cost-efficient and simplemanufacturability.

DESCRIPTION OF FURTHER EXEMPLARY EMBODIMENTS

In the following, further exemplary embodiments of the package, theelectronic device, the vehicle, and the methods will be explained.

In an embodiment, the material of the shielding layer is configured toprovide at least one property/function of the group consisting of:

-   -   corrosion resistance (i.e. providing protection against        undesired corrosion);    -   impermeability for liquids (i.e. preventing ingress of a liquid        into the encapsulant, in particular being waterproof);    -   abrasion resistance (i.e. preventing flowing cooling fluid from        removing surface material of the package by abrasion); and    -   fissure bridging capability (i.e. being capable of bridging a        crack or fissure which may occur under undesired circumstances        in the package, for instance as a consequence of excessive        thermal or mechanical load).

In an embodiment, the material of the shielding layer comprises at leastone of the group consisting of:

-   -   an organic dielectric material, in particular parylene or        another plastic material;    -   an organic electrically conductive material, in particular an        electrically conductive polymer;    -   an inorganic dielectric material, in particular a        low-temperature glass or a ceramic; and    -   a metallic material, in particular at least one of titanium,        nickel, aluminum, titanium-nickel, titanium-aluminum, and        titanium-aluminum-nickel.

However, other materials being fluid tight (in particular liquid tight)and being therefore capable of shielding the cooling fluid with regardto the encapsulant of the package may be used as well for the shieldinglayer(s).

In an embodiment, the package comprises a first heat removal bodythermally coupled to a first main surface of the at least one electronicchip and configured for removing thermal energy from the at least oneelectronic chip to the cooling fluid. The first heat removal body may bepartly (in particular only partly, so that the first heat removal bodyforms part of an exterior surface of the package, which is advantageousin terms of its heat removal capability) encapsulated by theencapsulant. In other words, the package may comprise at least one heatremoval body being partially embedded in the package and partiallyexposed to a cooling cavity. The first heat removal body may have thefunction of efficiently removing heat generated by the at least oneelectronic chip mounted thereon. Thus, the first heat removal body maysimultaneously also serve as a chip carrier.

In an embodiment, the package comprises a second heat removal bodythermally coupled to a second main surface of the at least oneelectronic chip and/or of at least one further electronic chip of thepackage and configured for removing thermal energy from the at least oneelectronic chip and/or from the at least one further electronic chip tothe cooling fluid. The second heat removal body may be partly (inparticular only partly, so that the second heat removal body forms partof an exterior surface of the package, which is advantageous in terms ofits heat removal capability) encapsulated by the encapsulant. Theprovision of a second heat removal body in addition to the first heatremoval body provides the opportunity for highly efficient double-sidedcooling. In one alternative (as shown for instance in FIG. 1 and FIG. 2)each of one or more electronic chips may be coupled with a respectivefirst main surface thereof to the first heat removal body and may becoupled with the respective second main surface thereof to the secondheat removal body. In another alternative (not shown in the figures), atleast one electronic chip may be coupled only with the first heatremoval body, and at least one other electronic chip may be coupled onlywith the second heat removal body. In such a configuration, thementioned electronic chips may be arranged to face one another, whereasthe heat removal bodies may be arranged to oppose one another, therebyalso allowing for double sided cooling of the package.

In an embodiment, the first heat removal body (and/or an optional secondheat removal body) may comprise a material having a high thermalconductivity so as to be capable of efficiently removing heat from theone or more electronic chips to an environment of the package. Inparticular, the thermal conductivity of at least one of the heat removalbodies as a whole or a material thereof may be at least 10 W/mK, inparticular at least 50 W/mK.

In an embodiment, at least a portion of a surface of at least one of thefirst heat removal body and the second heat removal body is covered bypart of the shielding layer(s) (i.e. by the same shielding layer(s)which also cover(s) the encapsulant) or by at least one furthershielding layer (i.e. by one or more separate shielding layer(s) beingdifferent from the shielding layer(s) which cover(s) the encapsulant).In one configuration, it is highly efficient to manufacture a singlecommon shared and seamless shielding layer covering both the encapsulantand the respective heat removal body. A scenario in which additionalcoverage of a respective heat removal body with a shielding layer may bedesirable is a situation where undesired electrochemical interaction mayoccur when for example a copper surface layer of the heat removal body(for instance a copper layer of a DCB substrate) is arranged close tocooling fins made of another material such as aluminum. The shieldinglayer may then also function to electrochemically passivate theelectrochemically active metal surface(s).

In an embodiment, the encapsulant encapsulates at least one of part ofthe first heat removal body and part of the second heat removal body. Insuch a configuration, part of the exterior surface of the package isformed by a respective one of the heat removal bodies, which results ina highly efficient heat removal (since the encapsulant usually has asmaller thermal conductivity than the heat removal body or bodies).

In an embodiment, the package comprises a chip carrier on which the atleast one electronic chip is mounted. In particular, the first heatremoval body may be configured as the chip carrier (in addition to itsfunction as heat sink). For instance, at least one of the first heatremoval body and the second heat removal body may be configured as atleast one of the group consisting of a Direct Copper Bonding substrate(DCB), and a Direct Aluminum Bonding substrate (DAB). Alternative chipcarriers which may be used for other embodiments can be any interposerlike a substrate, a ceramic substrate, a laminar substrate, a leadframe,an IMS (Insulated Metal Substrate), a PCB (printed circuit board), etc.

In an embodiment, the package comprises a spacer body, in particular athermally conductive spacer body, arranged between the electronic chipand the second heat removal body. For example, such an optional spacerbody may be embodied as a copper block.

In an embodiment, at least one of the first heat removal body and thesecond heat removal body comprises an electrically insulating (andpreferably highly thermally conductive) layer having a first mainsurface covered by a first electrically conductive layer and having asecond main surface covered by a second electrically conductive layer.For example, the electrically insulating layer may be simultaneouslyhighly thermally conductive, which can be accomplished for example bythe provision of a ceramic layer. At least one of the electricallyconductive layers may be a copper layer combining a high thermalconductivity with a high electrical conductivity. However, aluminum isalso a proper material selection for at least one of the electricallyconductive layers. For instance, at least one of the first heat removalbody and the second heat removal body may be configured as at least oneof the group consisting of a Direct Copper Bonding substrate (DCB), anda Direct Aluminum Bonding substrate (DAB).

In an embodiment, at least one of the first heat removal body and thesecond heat removal body comprises an electrically conductive wiringstructure electrically connecting the electronic chip(s). In particular,the electrically conductive wiring structure may be one of theabove-mentioned first and second electrically conductive layers, whichmay be patterned in accordance with a required electric coupling logic.

In an embodiment, the package comprises a cooling fin body on at leastone of the first heat removal body and the second heat removal body.Such a cooling fin body may for instance be embodied by ribbon bonds ofa highly thermally conductive material such as aluminum. Alternatively,such a cooling fin body may also be embodied by an array of (forinstance matrix-like arranged) posts of a highly thermally conductivematerial such as aluminum. In an embodiment, the cooling fin body may beshaped so as to force the cooling fluid onto a nonlinear flow path, inparticular for generating vortex or other kind of flow turbulence. Thismay improve the thermal exchange between the package and the coolingfluid.

In an embodiment, the package comprises a shielding layer on at leastpart of an external surface of the cooling fin body. By covering alsothe cooling fin body partly or completely by a shielding layer of theabove described type, any undesired electrochemical interaction betweena surface metal of the cooling fin and a surface metal of a respectiveheat removal body, etc., can be avoided.

In an embodiment, the encapsulant is covered by the shielding layer in asurface region directly adjacent to at least one of the first heatremoval body and the second heat removal body. Thus, an uninterruptedsurface area may be formed in which the cooling fluid is incapable ofingressing into the package, which is neither enabled by the surfaceportion defined by the shielding layer on the encapsulant nor enabled bythe surface portion defined by the heat removal body.

In an embodiment, the package comprises an electrically conductivecontact structure, in particular a leadframe, extending partially withinand partially outside (in particular forming one or more exposed leads)of the encapsulant and being electrically coupled with the at least oneelectronic chip (for instance by wire bonding). By such an electricallyconductive contact structure, the at least one electronic chip may becoupled to an electronic environment of the package. For this purpose,one or more legs of the electrically conductive contact structure mayextend beyond the encapsulant. A leadframe may be a metal structurepartially inside a chip package that is configured for carrying signalsfrom the electronic chip to the outside, and/or vice versa. Theelectronic chip inside the package or electronic component may beattached to the leadframe, and then bond wires may be provided forattaching pads of the electronic chip to leads of the leadframe.Subsequently, the leadframe may be molded in a plastic case or any otherencapsulant.

In a preferred embodiment, the encapsulant is a mold compound. For theencapsulating by molding, a plastic material or a ceramic material maybe used. The encapsulant may comprise an epoxy material. Fillerparticles (for instance SiO₂, Al₂O₃, Si₃N₄, BN, AIN, diamond, etc.), forinstance for improving thermal conductivity may be embedded in anepoxy-based matrix of the encapsulant.

In an embodiment, the package comprises at least one heat removal bodyeach thermally coupled to a respective main surface of at least one ofthe at least one electronic chip and configured for removing thermalenergy from the respective at least one electronic chip to the coolingfluid, wherein the cooling cavity is delimited (in particularexclusively, i.e. without further cavity delimiting constituents) by thecooling member, by the shielding layer on the encapsulant (with orwithout sealing ring thereon) and by the at least one heat removal body(with or without shielding layer thereon). Different heat removal bodiesmay serve the same electronic chips (as shown in FIG. 1 and FIG. 2) ormay serve different electronic chips in terms of thermally coupling themwith cooling fluid. This allows for a proper heat exchange betweencooling fluid and package and additionally allows to keep the dimensionof the in many cases costly heat removal body or bodies small.

In an embodiment, the shielding layer on at least part of an externalsurface of the encapsulant is configured for shielding an interior ofthe package with regard to cooling fluid. For instance, such a coolingfluid can be a cooling liquid like water.

In an embodiment, the encapsulant, in particular a portion of theencapsulation covered with a shielding layer, is provided with astructural feature contributing to a cooling fluid related function. Inparticular, such at least one structural feature may comprise a sealinggroove for accommodating a sealing member for promoting fluid-tightnessof the cooling cavity, and/or may comprise a cooling fluid guidingstructure for guiding the cooling fluid along a defined flow path. Thus,the provision of the shielding layer does not negatively influence thepossibility of defining one or more structural features by acorresponding shaping of the encapsulant. By arranging a sealing O-ringon the shielding layer coated encapsulant rather than on a heat removalbody surface, costly heat removal body surface may be saved. Forinstance, such a sealing O-ring may be inserted by molding. By definingflow channels by a corresponding adjustment of the shape of theencapsulant, an undesired high flow resistance of the cooling fluid maybe prevented. When the cooling fluid is driven by a pump, the drivepower for the pump may be thereby reduced advantageously.

In an embodiment, the cooling member is configured for being mounted onthe package for double-sided cooling of the package by cooling fluidbeing thermally couplable with two opposing main surfaces of thepackage. This results in a particularly pronounced cooling performance.However, according to another exemplary embodiment, also single-sidedcooling may be accomplished.

In an embodiment, the cooling member comprises at least one of a coolingmedium supply channel configured for supplying cooling medium from acooling fluid reservoir to the cooling cavity, and a cooling mediumdrain channel configured for draining cooling medium from the coolingcavity. The flow trajectory of cooling fluid may therefore be preciselydefined. Preferably, a closed loop cooling fluid flow path may bedesigned.

In an embodiment, the heat removal body and the cooling member are freeof a direct mutual contact. A direct contact with the heat removal bodymay be accomplished by the shielding layer spacing the encapsulant withregard to the cooling member.

In an embodiment, the shielding layer is manufactured by at least one ofthe group consisting of:

-   -   sputtering;    -   deposition (in particular chemical deposition (such as plating)        or deposition by evaporation, vapor deposition);    -   chemical vapor deposition (CVD);    -   low-temperature melting, in particular by laser processing;    -   varnishing; and    -   plasma deposition.

However, other manufacturing procedures are possible as well.

In an embodiment, the method comprises conditioning the encapsulant (inparticular by roughening a surface of the encapsulant) for promoting itsadhesion properties prior to forming the shielding layer on theencapsulant. In particular by roughening the surface of the encapsulantbefore formation of the shielding layer may improve adhesion.Additionally or alternatively, waxy material may be removed from theencapsulant (such as a mold compound), also to improve adhesion.

In an embodiment, the electronic chip is configured as a powersemiconductor chip. Thus, the electronic chip (such as a semiconductorchip) may be used for power applications for instance in the automotivefield and may for instance have at least one integrated insulated-gatebipolar transistor (IGBT) and/or at least one transistor of another type(such as a MOSFET, a JFET, etc.) and/or at least one integrated diode.Such integrated circuit elements may be made for instance in silicontechnology or based on wide-bandgap semiconductors (such as siliconcarbide, gallium nitride or gallium nitride on silicon). A semiconductorpower chip may comprise one or more field effect transistors, diodes,inverter circuits, half-bridges, full-bridges, drivers, logic circuits,further devices, etc.

In an embodiment, the electronic chip experiences a vertical currentflow. The package architecture according to exemplary embodiments of theinvention is particularly appropriate for high power applications inwhich a vertical current flow is desired, i.e. a current flow in adirection perpendicular to the two opposing main surfaces of theelectronic chip, one of which being used for mounting the electronicchip on the carrier.

In embodiments, the electronic component may be configured as a halfbridge, a cascode circuit, a circuit constituted by a field effecttransistor and a bipolar transistor being connected in parallel to oneanother, or a power semiconductor circuit. Therefore, the packagingarchitecture according to exemplary embodiments is compatible with therequirements of very different circuit concepts.

In an embodiment, the electronic component is configured as one thegroup consisting of a leadframe connected power module, a TransistorOutline (TO) electronic component, a Quad Flat No Leads Package (QFN)electronic component, a Small Outline (SO) electronic component, a SmallOutline Transistor (SOT) electronic component, and a Thin More OutlinePackage (TSOP) electronic component. Therefore, the electronic componentaccording to an exemplary embodiment is fully compatible with standardpackaging concepts (in particular fully compatible with standard TOpackaging concepts) and appears externally as a conventional electroniccomponent, which is highly user-convenient. In an embodiment, theelectronic component is configured as power module, e.g. molded powermodule. For instance, an exemplary embodiment of the electroniccomponent may be an intelligent power module (IPM).

As substrate or wafer forming the basis of the electronic chips, asemiconductor substrate, preferably a silicon substrate, may be used.Alternatively, a silicon oxide or another insulator substrate may beprovided. It is also possible to implement a germanium substrate or aIII-V-semiconductor material. For instance, exemplary embodiments may beimplemented in GaN or SiC technology.

Furthermore, exemplary embodiments may make use of standardsemiconductor processing technologies such as appropriate etchingtechnologies (including isotropic and anisotropic etching technologies,particularly plasma etching, dry etching, wet etching), patterningtechnologies (which may involve lithographic masks), depositiontechnologies (such as chemical vapor deposition (CVD), plasma enhancedchemical vapor deposition (PECVD), atomic layer deposition (ALD),sputtering, etc.).

The above and other objects, features and advantages of the presentinvention will become apparent from the following description and theappended claims, taken in conjunction with the accompanying drawings, inwhich like parts or elements are denoted by like reference numbers.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of exemplary embodiments and constitute a part of thespecification, illustrate exemplary embodiments.

In the drawings:

FIG. 1 shows a cross-sectional view of an electronic device with adouble-sided cooling package according to an exemplary embodiment.

FIG. 2 shows a cross-sectional view of an electronic device with adouble-sided cooling package according to another exemplary embodiment.

FIG. 3 shows a three-dimensional view of a double-sided cooling packagewithout metallization according to an exemplary embodiment.

FIG. 4 shows a three-dimensional view of a double-sided cooling packagewith metallization according to an exemplary embodiment.

FIG. 5 shows a schematic view of a vehicle with an electronic devicecomprising a package according to an exemplary embodiment.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

The illustration in the drawing is schematically.

Before describing further exemplary embodiments in further detail, somebasic considerations of the present inventors will be summarized basedon which exemplary embodiments have been developed which provide for anefficient cooling of a reliable package.

According to an exemplary embodiment of the invention, a package, inparticular a molded power module, is provided which is equipped with anefficient heat removal mechanism by direct fluid (in particular liquid)cooling without any risk of undesired penetration of cooling fluid intousually not waterproof encapsulant material.

The demand for an increased compactness of packages in combination withthe demand for package manufacturability with low effort bringsconventional cooling concepts for removing energy generated duringoperation of a package to the limit. This particularly holds for moldedpower modules with Direct Copper Bonding (DCB) substrate used forremoving heat from the encapsulated chip(s). A severe limitation is thehigh cost of DCB area of a package. This particularly holds for adouble-sided cooling architecture where two such DCB substrates or otherheat removal bodies are implemented.

An exemplary embodiment of the invention provides a package with adirect cooling configuration using a heat removal body architecture (inparticular implementing one or more DCBs), preferably but notnecessarily in terms of double-sided cooling, which allows efficientremoval of generated heat while safely preventing any undesiredintrusion of cooling fluid into a mold-type encapsulant of the package.This can be accomplished by arranging a shielding layer at least oncooling fluid exposed surface portions of the encapsulant, i.e. spatialareas of the package external surface being not formed by the heatremoval body or bodies and being in physical contact with the coolingfluid during operation. In order to prevent the cooling medium fromdiffusing or flowing into an interior of the package or power module,the sealing shielding layer may be arranged directly on the (forinstance mold compound type) encapsulant material. Advantageously, theshaping of the encapsulant may be adjusted to provide a flow guidance soas to precisely define fluidic paths along which the cooling fluid canflow.

In an embodiment, the shielding layer is a metal layer covering one ormore surface portions of the encapsulant for preventing fluidcommunication of the cooling fluid up to the encapsulant. The shieldinglayer can be formed by sputtering, vapor deposition (in particularchemical vapor deposition (CVD)), melting at moderate temperature, usinga laser, varnishing and/or plasma deposition. The material of theshielding layer may be an organic isolation material (such as parylene),an inorganic isolation material (such as a low-temperature glass) or ametallic layer (for instance titanium, nickel, aluminum,titanium/nickel, titanium/aluminum, titanium/aluminum/nickel, etc.).

By taking these measures, the in many cases costly material of a heatremoval body (in particular a ceramic material of a DCB) may be reducedin size, since even shielding layer covered surface portions of theencapsulant can be brought in direct contact with a liquid or gaseouscooling fluid.

Moreover, one or more structures (such as indentations and/orprotrusions) can be formed in the mold tool and can be manufacturedwithout additional effort during encapsulation. Such structures are anindentation for an O-ring sealing, an indentation for cooling fluid flowpath definition, etc.

According to an exemplary embodiment, a package (in particular a powermodule) may be provided with a direct heat removal body (in particularDCB) cooling capability, wherein the area enclosed by a cooling body maybe larger than the area of the heat removal body (and may be larger thanthe area of one or more electronic chips and/or of one or more optionalspacer bodies). A thin shielding layer may be provided which shields orseals the region of the encapsulant (in particular mold body) exposedoutside of the heat removal body with regard to the cooling fluid.Advantageously, the shielding layer may be corrosion resistant and/orwaterproof and/or abrasion resistant and/or fissure bridging. Theshielding layer may be composed of one or several sub-layers and mayenclose cooling structures (such as cooling fins) on the heat removalbody. The (preferably mold-type) encapsulant may be simultaneously usedfor structurally defining sealing areas and/or may provide for flowguidance.

FIG. 1 shows a cross-sectional view of an electronic device 150 with adouble-sided cooling package 100 according to an exemplary embodiment.The electronic device 150 is composed of a power package 100 and atwo-piece cooling member 152.

The cooling member 152 is configured as a two-piece shell (i.e.comprising an upper shell and a lower shell between which the package100 is sandwiched) for being mounted on the package 100 to therebydelimit, together with the package 100, a cooling cavity 154 fortemporarily accommodating flowing cooling fluid for cooling the package100. As can be taken from FIG. 1, the cooling member 152 is mounted onthe package 100 for double-sided cooling of the package 100 by coolingfluid being thermally couplable with two opposing main surfaces of thepackage 100.

The package 100 according to FIG. 1 comprises two electronic chips 102which are here embodied as power semiconductor chips. The electronicchip 102 shown on the left hand side of FIG. 1 may be a diode chip,whereas the electronic chip 102 shown on the right-hand side of FIG. 1may be an IGBT (Insulated Gate Bipolar Transistor) chip.

A first heat removal body 108, which is here embodied as Direct CopperBonding (DCB) substrate, is thermally and mechanically coupled to afirst main surface of the electronic chips 102 and forms part of anexterior surface of the package 100. The first heat removal body 108 isconfigured for removing thermal energy from the electronic chips 102during operation of the package 100 to cooling liquid (not shown, forinstance water and/or an organic solvent such glycol) supplied to thecooling cavity 154 between the package 100 and the package externalcooling member 152. The first heat removal body 108 comprises a centralelectrically insulating and thermally conductive layer 112, here made ofceramic material, having a first main surface covered by a firstelectrically conductive layer 114, which is here embodied as a copperlayer, and having an opposing second main surface covered by a secondelectrically conductive layer 116, which is here embodied as a furthercopper layer. The electronic chips 102 are mounted and soldered on thefirst heat removal body 108 and may be electrically connected with thesecond electrically conductive layer 116 by bond wires (not shown).Hence, the first heat removal body 108 functions as a chip carrier andas a heat sink. The first electrically conductive layer 114 of the firstheat removal body 108 forms part of an exterior surface of the package100 and thereby significantly contributes to the heat removal from theelectronic chips 102 during operation of the package 100.

Optional spacer bodies 130, which may be embodied as copper blocks, aresoldered onto upper main surfaces of the electronic chips 102.

Moreover, a second heat removal body 110 is thermally coupled to asecond main surface of the electronic chips 102 via the spacer bodies130. Also the second heat removal body 110 comprises a centralelectrically insulating and thermally conductive layer 112, which may bemade of a ceramic, having a first main surface covered by a firstelectrically conductive layer 114, which is here embodied as a copperlayer, and having an opposing second main surface covered by a secondelectrically conductive layer 116, which is here embodied as a furthercopper layer. The second electrically conductive layer 116 of the secondheat removal body 110 is soldered onto the spacer bodies 130. The firstelectrically conductive layer 114 of the second heat removal body 110forms part of an exterior surface of the package 100 and therebysignificantly contributes to the heat removal from the electronic chips102 during operation of the package 100. As a whole, the second heatremoval body 110 is configured as a heat sink for removing thermalenergy from the electronic chips 102.

Hence, the heat removal bodies 108, 110 are both partially embedded inthe package 100 and partially exposed to the cooling cavity 154.Furthermore, the heat removal bodies 108, 110 and the cooling member 152are free of a direct mutual contact.

An electrically conductive contact structure 118, here embodied as aleadframe, extends partially within and partially outside of theencapsulant 104 and may be electrically coupled with the electronicchips 102 for example via a connection with the second electricallyconductive layer 116 of the first heat removal body 108 (for example viaa solder connection, using bond wires, etc.).

Furthermore, the package 100 comprises a mold-type encapsulant 104encapsulating the electronic chips 102, the spacer bodies 130, only partof the electrically conductive contact structure 118, only part of thefirst heat removal body 108 and only part of the second heat removalbody 110. The part of the electrically conductive contact structure 118encapsulated by the encapsulant 104 serves for electrically contactingthe electronic chips 102, whereas another part of the electricallyconductive contact structure 118 exposed from the encapsulant 104provides one or more leads for connection with an electronic peripherydevice (not shown). Since the electrically conductive contact structure118 extends partially within and partially outside of the encapsulant104 and is electrically coupled with the electronic chips 102, it iscapable of providing an electric coupling between an exterior and aninterior of the package 100.

As can be taken from FIG. 1, the package 100 may comprise one or moreshielding layers 106 covering several surface portions of theencapsulant 104, which surface portions delimit part of the coolingcavity 154. The encapsulant 104 is covered by the shielding layers 106also in surface regions directly adjacent to the first heat removal body108 and to the second heat removal body 110. The cooling cavity 154 canbe denoted as the hollow volume through which a liquid cooling fluid canbe guided for cooling the package 100 during operation. Apart from theshielding layers 106, the cooling cavity 154 is also delimited by thecooling member 152 as well as by the exposed surfaces of the first heatremoval body 108 and the second heat removal body 110. The shieldinglayers 106 may be made of a metallic material such as nickel which isconfigured for shielding an interior of the package 100 with regard tocooling liquid, i.e. to provide a sealing barrier preventing the coolingliquid from ingressing the interior of the package 100. In other words,the shielding layers 106 are impermeable for the cooling liquid such aswater and thereby prevent that moisture enters the package 100. Thus,undesired effects (such as delamination at package internal materialinterfaces, reduced electrical reliability, etc.) resulting from liquidentering in particular the encapsulant 104 can be safely prevented orstrongly suppressed. Advantageously, the shielding layers 106 cover themold-type encapsulant 104 which is specifically prone for being soakedwith cooling liquid such as water. As a consequence of the provision ofthe shielding layers 106 covering the liquid sensitive encapsulant 104,the size of the costly heat removal bodies 108, 110 may be kept small,since also the locally shielded encapsulant 104 may contribute todelimiting of the cooling cavity 154.

Moreover, portions of the encapsulant 104 covered with the shieldinglayers 106 are provided with a structural feature 159 contributing to acooling fluid related function. More specifically, this structuralfeature 159 is a sealing groove for accommodating a sealing member 156,embodied as O-ring, for promoting fluid-tightness of the cooling cavity152.

A respective cooling fin body 158 is arranged on each of the first heatremoval body 108 and the second heat removal body 110. The cooling finbodies 158 may be thermally highly conductive structures (for instancemade of aluminum) being shaped (for instance with a zig-zag shape asshown in FIG. 1) so as to produce turbulent flow or vortex in thecooling liquid flowing along the cooling cavity 154. This improves theheat exchange between the package 100 and the cooling fluid and therebyimproves the heat removal capability.

As can be taken from FIG. 1, further shielding layers 106 may cover anexternal surface of the cooling fin bodies 158 partly or entirely. Thisallows to prevent undesired electrochemical effects which may occur forexample when the material of the cooling fin bodies 158 (for instancealuminum) and exposed material of the heat removal bodies 108, 110 (forinstance copper) differ.

Still referring to FIG. 1, additional shielding layers 106 may beprovided to cover portions of a surface of the first heat removal body108 and the second heat removal body 110. Also this measure contributesto the suppression of undesired electrochemical effects which may occurfrom different uncovered metallic surfaces within the cooling cavity154.

It should be understood that, although some of the shielding layers 106only partly cover the respective surfaces (of the heat removal bodies108, 110, of the cooling fin bodies 158), it is alternatively alsopossible that their entire surfaces are covered by shielding layers 106.Correspondingly, although the entire surfaces of the encapsulant 104exposed within the cooling cavity 154 are covered by correspondingshielding layers 106 according to FIG. 1, it is also possible in otherembodiments that these shielding layers 106 cover the mentioned surfacesonly partly. In particular the heat removal bodies 108, 110 may be alsocompletely uncovered from shielding layers 106.

FIG. 2 shows a cross-sectional view of an electronic device 150 with adouble-sided cooling package 100 according to another exemplaryembodiment.

According to FIG. 2, portions of the encapsulant 104 covered with theshielding layers 106 are provided with a further structural feature 159contributing to a cooling fluid related function. More specifically,this additional structural feature 159 is a cooling fluid guidingstructure or flow guiding structure for guiding the cooling fluid alonga defined flow path for keeping the flow resistance small.Correspondingly, the cooling member 152 comprises cooling medium supplychannels 160 configured for supplying cooling medium to the coolingcavity 154, and cooling medium drain channels 162 configured fordraining cooling medium from the cooling cavity 154. Arrows in FIG. 2indicate the flow direction of cooling liquid.

FIG. 3 shows a three-dimensional view of a preform of a double-sidedcooling package 100 without metallization according to an exemplaryembodiment. Thus, FIG. 3 shows a preform of package 100 after havingpartly embedded the heat removal bodies 108, 110 and the electricallyconductive contact structure 118 in the encapsulant 104 and prior to theformation of the shielding layer(s) 106.

FIG. 4 shows a three-dimensional view of double-sided cooling package100 with metallization according to an exemplary embodiment. In order toobtain the package 100 shown in FIG. 4 from the preform shown in FIG. 3,the illustrated metallic shielding layer 106 has been formed, forinstance by chemical vapor deposition (CVD).

FIG. 5 shows a schematic view of a vehicle 170 with an electronic device150 comprising a package 100 according to an exemplary embodiment.

More specifically, the power package 100 may form part of a controlblock 192 controlling operation of engine/battery block 194. Hence, apackage 100 or power module according to an exemplary embodiment of theinvention may be used for an automotive application. A preferredapplication of such a power package 100 is an implementation as aninverter circuit or inverted rectifier for vehicle 170 which may be anelectrically driven vehicle or which may be a hybrid vehicle. Such aninverter may transfer a direct current (DC) of the battery into analternating current (AC) for driving the electric engine of vehicle 170.In a hybrid vehicle, it is also possible to at least partially recovermechanical energy and to transfer it, by the inverter, back intoelectric energy to recharge the battery. In such an automotive inverterapplication, extreme amounts of heat are generated during operation ofthe power package 100. This heat can be efficiently removed by thedouble-sided cooling concept described above. However, it should be saidthat, in other embodiments, also single-sided cooling may be sufficient.

It should be noted that the term “comprising” does not exclude otherelements or features and the “a” or “an” does not exclude a plurality.Also elements described in association with different embodiments may becombined. It should also be noted that reference signs shall not beconstrued as limiting the scope of the claims. Moreover, the scope ofthe present application is not intended to be limited to the particularembodiments of the process, machine, manufacture, composition of matter,means, methods and steps described in the specification. Accordingly,the appended claims are intended to include within their scope suchprocesses, machines, manufacture, compositions of matter, means,methods, or steps.

What is claimed is:
 1. A package, comprising: at least one electronicchip; an encapsulant encapsulating at least part of the at least oneelectronic chip; a shielding layer on at least part of an externalsurface of the encapsulant configured for shielding an interior of thepackage with regard to cooling fluid for removing thermal energy fromthe at least one electronic chip.
 2. The package according to claim 1,wherein the material of the shielding layer is configured to provide atleast one property of the group consisting of: corrosion resistance;impermeability for a liquid, in particular for water and/or an organicsolvent such glycol; abrasion resistance; and fissure bridgingcapability.
 3. The package according to claim 1, wherein the material ofthe shielding layer comprises at least one of the group consisting of:an organic dielectric material, in particular parylene; an organicelectrically conductive material, in particular an electricallyconductive polymer; an inorganic dielectric material, in particular alow-temperature glass; and a metallic material, in particular at leastone of the group consisting of titanium, nickel, aluminum,titanium-nickel, titanium-aluminum, and titanium-aluminum-nickel.
 4. Thepackage according to claim 1, comprising a first heat removal bodythermally coupled to a first main surface of the at least one electronicchip and configured for removing thermal energy from the at least oneelectronic chip to the cooling fluid.
 5. The package according to claim4, comprising a second heat removal body thermally coupled to a secondmain surface of the at least one electronic chip or of at least onefurther electronic chip of the package and configured for removingthermal energy from the at least one electronic chip or from the atleast one further electronic chip to the cooling fluid.
 6. The packageaccording to claim 4, wherein at least a portion of a surface of atleast one of the first heat removal body and the second heat removalbody is covered by part of the shielding layer or by at least onefurther shielding layer.
 7. The package according to claim 4, wherein atleast one of the first heat removal body and the second heat removalbody comprises an electrically insulating layer having a first mainsurface covered by a first electrically conductive layer and having asecond main surface covered by a second electrically conductive layer.8. The package according to claim 4, comprising a cooling fin body on atleast one of the first heat removal body and the second heat removalbody.
 9. The package according to claim 8, comprising a shielding layeron at least part of an external surface of the cooling fin body.
 10. Thepackage according to claim 4, wherein the encapsulant is covered by theshielding layer in a surface region directly adjacent to at least one ofthe first heat removal body and the second heat removal body.
 11. Anelectronic device, comprising: a package according to claim 1; and acooling member configured for being mounted on the package to therebydelimit, together with the package, a cooling cavity for accommodatingcooling fluid for cooling the package.
 12. The electronic deviceaccording to claim 11, wherein the package comprises at least one heatremoval body each thermally coupled to a respective main surface of atleast one of the at least one electronic chip and configured forremoving thermal energy from the respective at least one electronic chipto the cooling fluid, wherein the cooling cavity is delimited, inparticular exclusively, by the cooling member, by the shielding layer onthe encapsulant and by the at least one heat removal body with orwithout shielding layer thereon.
 13. The electronic device according toclaim 11, wherein the encapsulant, in particular a portion of theencapsulant covered with the shielding layer, is shaped to form astructural feature contributing to a cooling fluid related function. 14.The electronic device according to claim 13, wherein the structuralfeature comprises at least one of the group consisting of: a sealinggroove for accommodating a sealing member for promoting fluid-tightnessof the cooling cavity; and a cooling fluid guiding structure for guidingthe cooling fluid along a defined flow path.
 15. The electronic deviceaccording to claim 11, wherein the cooling member is configured forbeing mounted on the package for double-sided cooling of the package bycooling fluid being thermally couplable with two opposing main surfacesof the package.
 16. The electronic device according to claim 11, whereinthe cooling member comprises at least one of a cooling medium supplychannel configured for supplying cooling medium to the cooling cavity,and a cooling medium drain channel configured for draining coolingmedium from the cooling cavity.
 17. A method of manufacturing a package,wherein the method comprises: encapsulating at least part of at leastone electronic chip by an encapsulant; forming a shielding layer on atleast part of an external surface of the encapsulant and configuring theshielding layer for shielding an interior of the package with regard tocooling fluid for removing thermal energy from the at least oneelectronic chip.
 18. The method according to claim 17, wherein theshielding layer is manufactured by at least one of the group consistingof: sputtering; deposition, in particular chemical deposition, such asplating, or deposition by evaporation; chemical vapor deposition;low-temperature melting, in particular by laser processing; varnishing;and plasma deposition.
 19. The method according to claim 17, wherein themethod comprises conditioning the encapsulant, in particular byroughening a surface of the encapsulant, for promoting its adhesionproperties prior to forming the shielding layer on the encapsulant. 20.A method of manufacturing an electronic device, wherein the methodcomprises: providing a package according to claim 1; and mounting acooling member on the package to thereby delimit, together with thepackage, a cooling cavity for accommodating cooling fluid for coolingthe package.
 21. A vehicle, comprising a package according to claim 1.22. A method of using an electronic device according to claim 11 for anautomotive application, in particular as an inverter circuit for an atleast partially electrically driven vehicle.